This core will provide a centralized service for producing the transgenic mice initially required in Program Projects 2, 3, and 4. Specifically, the core will undertake the following procedures: (1) microinjection of fertilized one-cell mouse eggs with purified DNA constructs prepared by Program Project investigators, (2) injection of ES cells into blastocyst, (3) return the eggs or blastocyst to pseudopregnant foster mothers, (4) screen for transgenic offspring by Southern analysis or PCR analysis of DNA isolated from tail, (5) organize the mating and pedigree analysis of transgenic mice, and (6) assist in the dissection and analysis of tissue from transgenic mice and embryos.